Overview

Graves' disease is the most common cause of hyperthyroidism, with conventional treatment options being anti-thyroid drugs (ATD), radioiodine (RAI) and surgery. For ATD, it has been the first-line treatment over decades. Despite its ability to induce remission, minor side effects such as skin rash, gastrointestinal disturbance and arthralgia occur in around 5% of patients, while serious adverse reactions including agranulocytosis and hepatotoxicity are potentially life threatening. Patients are usually treated with ATD for 12 to 18 months but the relapse rate was reported to be up to 50-60% which these patients would require more definitive treatment options with RAI or thyroidectomy. However, RAI is not preferable in patients with Graves' ophthalmopathy as it could further worsen eye symptoms. RAI may also cause hypothyroidism in a substantial proportion of patients, with a subsequent need for lifelong thyroxine replacement. As for thyroidectomy, it carries an overall 2-10% risk of complications including bleeding, transient or permanent recurrent laryngeal nerve injury and hypoparathyroidism. Due to the drawbacks of the various conventional treatment options, there has been increasing interest in the development of minimally invasive treatment alternatives in recent years. With the evolution of thermal ablative strategies, high-intensity focused ultrasound (HIFU) and radiofrequency ablation (RFA) have been reported as feasible treatment options for relapsed Graves' disease. There has also been increasing reports in the use of microwave ablation (MWA) in the treatment of benign thyroid nodules. MWA works via generation of electromagnetic field and is performed by inserting a microwave antenna into the thyroid gland percutaneously under ultrasound (USG) guidance. The active tip of the antenna causes oscillation of the surrounding water molecules which induces frictional heat and creates a thermal ablative effect. As compared to RFA, MWA is not affected by heat sink effect and may require a shorter treatment time. Similar to other thermal ablative approaches, MWA has the merits of avoiding surgical scar, organ preservation as well as being an ambulatory procedure.

Eligibility

Inclusion Criteria:

• (a) age older than 18 years,
• (b) relapsed Graves' disease despite an adequate ATD treatment for 18 months or more
• (c) absence of vocal cord immobility

Exclusion Criteria:

• (a) patients who prefer or are indicated for surgery,
• (b) presence of head and/or neck disease preventing hyperextension of the neck,
• (c) history of thyroid cancer or other malignant tumours in the neck region,
• (d) history of neck irradiation,
• (e) severe Graves' ophthalmopathy,
• (f) large compressive goitre,
• (g) pregnancy or lactation, and
• (h) any contraindication to intravenous sedation.